Foam Board Insulation

Foam boards—rigid panels of insulation—can be used to insulate almost any part of your home, from the roof down to the foundation. They provide good thermal resistance and often add structural strength to your home. Foam board insulation sheathing reduces heat conduction through structural elements, like wood and steel studs.

Extruded expanded polystyrene (XEPS) is a closed-cell foam insulation. To make it, the polystyrene pellets are mixed with various chemicals to liquefy them. A blowing agent is then injected into the mixture, forming gas bubbles. The foaming, thick liquid is then forced through a shaping die. When cooled, the panel is cut as required. Foam densities are typically 1.5 pounds per cubic foot (24 kilograms per cubic meter).

The R-value depends upon the density of the material and is generally about R-5 per inch. It’s also much more consistent in density, making it better suited for use on roofs or for wall panels. Extruded polystyrene also has excellent resistance to moisture absorption.